20 Tests
Air Brakes Endorsement Test Online | District Of Columbia 2021
Train for FREE online with our District Of Columbia CDL air brake test. The official exam test consists of several obligatory parts, with all of them checking your knowledge of different blocks of road rules. If you need to obtain a DC Class A/Class B driver license in 2021, practice as much as possible. Free sample tests published on our website will help you check and improve your knowledge and boost your grades. Please bear in mind that the requirements for CDL may vary from state to state.
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1 . How is the parking brake released?
By tapping the accelerator twice
In newer vehicles with air brakes, the parking brakes are controlled by a diamond-shaped yellow knob. Pull the knob out to activate the parking brakes and push it in to release them.
2 . Pressing and releasing a brake pedal unnecessarily can:
Create a loud noise.
In an air brake system, pressing and releasing the brake pedal unnecessarily can release air from the braking system faster than the compressor can replace it.
3 . Most heavy-duty vehicles use:
Quadruple air brake systems.
Most heavy-duty vehicles use dual air brake systems, in which there are two separate braking systems operated by a single set of controls. Each system operates the brakes on different axles.
4 . Emergency brakes are:
Only required when transporting hazardous materials.
All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes.
5 . Brakes may get out of adjustment:
If they get wet.
Brakes can get out of adjustment quickly, especially if they are used to the point of overheating. Brake adjustment should be checked frequently.
6 . What can happen if parking brakes are used in very wet weather with temperatures below freezing?
The brakes may become too smooth to be used.